X-Ray CT Apparatus, Image Processing Apparatus, and Image Processing Method

1. An X-ray CT apparatus comprising: acquiring circuitry configured to count photons derived from X-rays that have passed through a subject and to acquire a result obtained by discriminating energy levels of the counted photons as a counting result; and processing circuitry configured to set an energy dividing set by setting one or more energy discrimination regions having a fine granularity level in an energy region positioned near a characteristic energy value indicating the X-ray absorption characteristic of a substance designated by an operator and by setting one or more energy discrimination regions having a coarse granularity level in an energy region other than the energy region, to notify the acquiring circuitry of the energy dividing set, to receive the counting result acquired by the acquiring circuitry by allocating a counted value to each of a plurality of energy discrimination regions that are set in the energy dividing set, and to reconstruct image data by using the received counting result.

2. The X-ray CT apparatus according to claim 1 , wherein the processing circuitry is configured to set the energy dividing set in a region excluding regions positioned before and after the characteristic energy value.

3. The X-ray CT apparatus according to claim 1 , wherein, if a plurality of substances are designated by the operator, the processing circuitry is configured to set the energy dividing set by setting a plurality of energy discrimination regions according to a characteristic energy value indicating an X-ray absorption characteristic of each of the substances.

4. The X-ray CT apparatus according to claim 3 , wherein the processing circuitry is configured to set the energy dividing set for each of the plurality of substances, by further bundling the plurality of energy discrimination regions with a plurality of energy discrimination regions having a coarse granularity level in accordance with the characteristic energy value of each of the plurality of substances.

5. The X-ray CT apparatus according to claim 4 , wherein the processing circuitry is configured to set the energy dividing set for each of the plurality of substances in a region excluding regions positioned before and after the characteristic energy value of each of the plurality of substances.

6. The X-ray CT apparatus according to claim 1 , wherein the processing circuitry is configured to set the energy dividing set prior to the acquisition of the counting result.

7. The X-ray CT apparatus according to claim 1 , wherein the processing circuitry is configured to set the energy dividing set by using a data memory circuitry storing therein information about an X-ray absorption spectrum of each of a plurality of substances.

8. The X-ray CT apparatus according to claim 1 , wherein the processing circuitry is configured to store setting values used for setting the energy dividing set into a predetermined storage circuitry so as to be associated with the corresponding substance and causes a display to display an operation button used for reading the setting values.

9. The X-ray CT apparatus according to claim 1 , wherein, if the energy dividing set has been changed based on a condition change performed by the operator, the processing circuitry is configured to store setting values used for resetting the energy dividing set in a predetermined storage circuitry so as to be kept the corresponding substance and to cause a display to display an operation button used for reading the setting values.

10. An image processing apparatus comprising: processing circuitry configured to set an energy dividing set by setting one or more energy discrimination regions having a fine granularity level in an energy region positioned near a characteristic energy value indicating the X-ray absorption characteristic of a substance designated by an operator and by setting one or more energy discrimination regions having a coarse granularity level in an energy region other than the energy region, to notify acquiring circuitry which is configured to count photons derived from X-rays that have passed through a subject and acquire a result obtained by discriminating energy levels of the counted photons as a counting result, of the energy dividing set, to receive the counting result acquired by the acquiring circuitry by allocating a counted value to each of a plurality of energy discrimination regions that are set in the energy dividing set, and to reconstruct image data by using the received counting result.

11. An image processing method comprising: performing a process by processing circuitry to set an energy dividing set by setting one or more energy discrimination regions having a fine granularity level in an energy region positioned near a characteristic energy value indicating the X-ray absorption characteristic of a substance designated by an operator and by setting one or more energy discrimination regions having a coarse granularity level in an energy region other than the energy region, to notify acquiring circuitry which is configured to count photons derived from X-rays that have passed through a subject and acquire a result obtained by discriminating energy levels of the counted photons as a counting result, of the energy dividing set, to receive the counting result acquired by the acquiring circuitry by allocating a counted value to each of a plurality of energy discrimination regions that are set in the energy dividing set, and to reconstruct image data by using the received counting result.